Neutralizing aliphatic acids containing froth-producing substances



Patented Nov. 28, 1933 T res 1,936,254 PAT 'r crrrca NEUTRALIZING ALIPHATIC. ACIDS coN ,TAINING FROTH PRODUCING SUB- STANCES Camille Dreyfus, New York, N.

Y., and Clifford I.

Haney, Brummondville, Quebec, Canada, assigners to Celanese Corporation of America, a p p is ccrporation of Delaware 1 No Drawing. Application July 11, 1930 Serial No. 467,391

11 Claims.

' or other lower aliphatic acids in an economical and expeditious manner. I i

A further object of our invention is to form alkalimetal acetates by the neutralization of the relatively dilute acetic acid obtained Whenwater is added to solutions of cellulose acetate in acetic acid to precipitate the cellulose acetate. Further objects of our invention will appear from the following detailed description.

In the formation of cellulose acetate or other organic esters of cellulose, the usual manner is to esterify the cellulose in the presence of the anhydride of the lower fatty acid corresponding to the cellulose ester to be formed and also in the presence of such lower fatty acid. When esterirfication is complete, the'cellulose ester dissolves in the lower fatty'acid'present. In order to'precipitate the cellulose ester, there is added at a subsequent stage ofthe process, water insufficient quantities to dilute the acid until it no longer retains the cellulose ester in solution, and

such as formic acid,'prop ionic acid or butyric acid.

In accordance with our invention, we neutralize relatively dilute solutions of lower fatty acids which contain froth-producing impurities by heating the same at elevated temperatures and then neutralizing them at such temperatures with an alkaline material, and then after settling, subjecting the solution to evaporation to recover the salts of the fatty acids. While' at present this invention is of greatest importance in connect-ion With the neutralization of dilute acetic acid ob tained after the acetylation of cellulose, it isap-= plicable to solutions of other lower fatty acids lhe invention is not confined to the neutraliza tion of such acids as are obtained from the esterif fication of cellulose, but is also applicableto the" neutralization of such acids obtained in any man ner. By relatively dilute solutions of the acids we intend to include solutions of 5,to' 50% or more concentration and particularly aqueous solutions of such acids.

As stated the relatively dilute solutions of the acids are heated at elevated temperatures, say

above 60 0., preferably between 90 and-100 C.

- The dilute acid solutions may be heated in a batch the dilute acid is separated from the precipitated cellulose ester.

However such dilute acid contains; either in suspension or in solution, certain organicmat-.

ters that cause frothing when-sodium carbonate is added thereto at room temperatures even while stirring. The froth so formed persists for hours and interferes with the'further working up of a solution of the metal salt thus formed on a commercial scale. Heretofore it has been theprac tice to distil the lower fatty acid, such as acetic acid, from such waste organic material, and then to neutralize the distillate. This distillation involves great expense, and moreover, even when copper stills are employed, the acid attacks the stills so that they depreciate rapidly.

-We have found that if such dilute lower fatty acid is neutralized, say with sodium carbonate,

while'at elevated temperatures, that the froth produced tends to breakdown quite readily, so that at such elevated temperatures, the neutralization can be carried outquickly enough for practical purposes. Contrary to expectation, there is noappreciable loss of acetic acid or other relatively volatile lower fatty acid during the neutralizing of the hot acid, owing to thefact that the froth that is formed acts as a fractionating column which permits only water vapor and carbondioxide to escape into the air,

liquor, so thatupon process in vessels of copper, wood, stainless steel and the like. If desired the process maybefa continuous one and thismay be done bypassing the solutions of the fatty acids through tubes or coils that are heated to the neutralizing vat.

For neutralizing the lower fatty acid, we prefer. to use sodium carbonate for economical reasons. However othercarbonates such as of potassium or calcium may be used as may the iii-carbonates v, v

of sodium and potassium. p H

During the neutralization'of the acid liquor, the organic products that are soluble in thedilute acid Often some of thisorganic material is so fine separate from the solution in a very fine form.

that it does notsettle outcompletely fromthe decantation it remains in the neutralized liquor and causes frothirig ofthe' same when it is evaporated. In such cases, we have found it preferable to add to the liquor. being neutralized small quantities of coagulatingagentssuch as soluble salts of aluminum and iron, examples of which are alum, aluminum sulfate, ferrous sulfate, ferric sulfate-or the doublesaltg of aluminum and ferric sulfate; liquor becomes slightly alkaline at the end of neutralization, these iron or aluminum compounds precipitate outas hydroxides and act as coagulants tobring down these organic bodies. J. In manycases there are enough organic impurities present in the dilute neutralizing'and act as coagulants for the gfine, organic precipitate, inwhich, case the additionof. other coagulantsis not'absolutely necessary.

As soon as the acid'which precipitate-out on time, the liquor does not cool to room tempera tures, but about one-half of the heat is. retained in the liquor when evaporationis commenced.

acid obtained from the precipitation of cellulose acetate, contains sulfuric acid that may have been employed as a catalyst, the same may be treated with the carbonate or hydroxide of barium to precipitate barium sulfate. However the removal of sulfuric acid is not absolutely necessary; since the sodium sulfate or potassium sulfate formed during neutralization does not form any scale in the evaporators.

In order further to illustrate our invention but without being limited thereto, thefollowing specific example is given.

7 Example Dilute acetic acid obtained from the precipitation of cellulose acetate by the addition of water to the acetylation mixture, and having a concentration of say 20%, is heated in a copper or wood container by means of a closed steam coil until it attains a temperature of 90 to 95 C. .When' this temperature is reached, the acid is run into a wooden neutralizing vat provided. with a me chanical agitator and asmall open steam connection. .As soon as the acid liquor starts to run into the 'vat, agitation is commenced and a small -amount of steam is injected into the liquor through the open steam connection to make up for the heat lost from the liquor to the vat and by radiation. maintained around 90 C.

While the acid is running into the vat the addition of soda ash (sodium carbonate) is commenced and additions of both the acid and soda ash is carried on in such a manner thatthe liquor in the neutralizing vat is kept almost at the neutral point. When the neutralizing vat is filled, aluminum sulfate .in amounts equal to about 0.015% of theliquor present is added. The

aluminum 'sulfateis usually added in the form of a solution ina small amount of water. The

. liquor in the vat is then tested and adjustments are made'so that it has a slightly alkaline reac--' tion'corresponding to an excess of 0.05' to 0.1% of sodium carbonate. g

lhe agitation is stopped after several minutes, 'and' the liquorinithe vat allowed to stand,

whereupon the precipitates settle, and after 12 hours or even less time, a liquor 7 or 8 feet'deep will have cleared. The sludge that collects at the bottom of the vat is not disturbed and the clear liquor is drawn off for evaporation. During the evaporation-no difiiculty with frothing is encountered; Without cleaning the vat, a number of-operations may beperformed, allowing the sludge torsettle each time, until it becomes severalinches deep, whereupon the sludge is removed-end a fresh series of operations commenced;

It is to'be understood that the foregoing example'xis'given merely by Way of illustration and that many variations may be made therein without departing from the spirit of our invention.

' Having described our invention, what we desire to secure by Letters Patent is:

1. Method of neutralizing a relatively dilute lower aliphatic acid containing a'froth-producing substancecomprising treating the-same at a tem The temperature of the acid is which generates gas upon neutralizing the acid. If the dilute acid to be neutralized, say acetic 3; Method of neutralizing a relatively dilute lower fatty acid recovered from the reaction mass "r'esulting'from the esterification of cellulose and containing a froth producing substance comprising treating the same at a temperature above C. with an alkaline substance which gencrates gas upon neutralizing the acid and then settling the resulting liquor.

4'. Method of neutralizing relatively dilute acetic acid recovered from the reaction mass resulting from the esterification of. cellulose and containing a froth producing substance comprising treating the same-at a temperature above 60C. with an alkaline substance which generates gas upon'neutralizing the acid and then settling .the resultingliquor.

5. 'Method "of neutralizing relatively dilute" acetic acidrecovered from the reaction mass resulting from the acetylation of cellulose and containing a froth-producing substance comprising treating the same with an alkaline carbonate at temperatures above 60 C. and then permitting the resulting liquor to settle.

6. Method of neutralizing relatively dilute acetic acid recovered from the reaction mass resulting from the acetylation of cellulose and containing a froth-producing substancecomprising treating. the same with an alkaline carbonate at temperatures between 90and' 100 C. and then permitting the resulting liquor to settle."

7.Method' of neutralizing a relativelydilute lower: fatty. acid containing a froth-producing substance comprising neutralizing the same at a temperature above 60? C. with an alkaline substance: which generates gas upon neutralizing with an alkaline, carbonate and towards the end of the reaction adding a coagulant thereto. 7 7 10. Method. of neutralizing relatively dilute acetic acid -recovered from the reaction mass resulting from the acetylation of cellulose and containing a froth-producing,substance comprising treating the same at a temperature above 60 C. withan alkaline carbonate and towards the end of the reactionadding a soluble iron compound.

1l.-Method of neutralizing relatively dilute acetic acid recovered from the reaction mass resulting from theacetylation of cellulose and con-- taining a froth-producing substance comprising treating the same at a temperature above 60 C.

with an alkaline carbonate and'towards the end of the reaction adding a soluble aluminum compound. 1

CAMILLE DRE YE US.

CLIFFORD I. HANEY. 

